Diff: BMP085.cpp

Revision:

0:6245372b9179

Child:

1:80e4c62baf09

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BMP085.cpp	Thu Oct 14 11:28:45 2010 +0000
@@ -0,0 +1,125 @@
+/*
+ * mbed library to use a Bosch Sensortec BMP085 sensor
+ * Copyright (c) 2010 Hiroshi Suga
+ * Released under the MIT License: http://mbed.org/license/mit
+ */
+
+#include "mbed.h"
+#include "BMP085.h"
+
+#define WEATHER_BMP085 0xee
+#define xpow(x, y) ((long)1 << y)
+
+
+BMP085::BMP085 (PinName p_sda, PinName p_scl, BMP085_oss p_oss) : i2c(p_sda, p_scl) {
+    init(p_oss);
+}
+
+BMP085::BMP085 (I2C& p_i2c, BMP085_oss p_oss) : i2c(p_i2c) { 
+    init(p_oss);
+}
+
+float BMP085::get_temperature() {
+    return temperature;
+}
+
+float BMP085::get_pressure() {
+    return pressure;
+}
+
+void BMP085::update () {
+    long t, p, ut, up, x1, x2, x3, b3, b5, b6;
+    unsigned long b4, b7;
+
+    twi_writechar(WEATHER_BMP085, 0xf4, 0x2e);
+    wait(0.01);
+    ut = twi_readshort(WEATHER_BMP085, 0xf6);
+
+    twi_writechar(WEATHER_BMP085, 0xf4, 0x34 | (oss << 6));
+    wait(0.05);
+    up = twi_readlong(WEATHER_BMP085, 0xf6) >> (8 - oss);
+
+    x1 = (ut - ac6) * ac5 / xpow(2, 15);
+    x2 = (long)mc * xpow(2, 11) / (x1 + md);
+    b5 = x1 + x2;
+    t = (b5 + 8) / xpow(2, 4);
+    temperature = (float)t / 10.0;
+
+    b6 = b5 - 4000;
+    x1 = (b2 * (b6 * b6 / xpow(2, 12))) / xpow(2, 11);
+    x2 = ac2 * b6 / xpow(2, 11);
+    x3 = x1 + x2;
+    b3 = ((((unsigned long)ac1 * 4 + x3) << oss) + 2) / 4;
+    x1 = ac3 * b6 / xpow(2, 13);
+    x2 = (b1 * (b6 * b6 / xpow(2, 12))) / xpow(2, 16);
+    x3 = ((x1 + x2) + 2) / xpow(2, 2);
+    b4 = ac4 * (unsigned long)(x3 + 32768) / xpow(2, 15);
+    b7 = ((unsigned long)up - b3) * (50000 >> oss);
+    if (b7 < (unsigned long)0x80000000) {
+        p = (b7 * 2) / b4;
+    } else {
+        p = (b7 / b4) * 2;
+    }
+    x1 = (p / xpow(2, 8)) * (p / xpow(2, 8));
+    x1 = (x1 * 3038) / xpow(2, 16);
+    x2 = (-7357 * p) / xpow(2, 16);
+    p = p + (x1 + x2 + 3791) / xpow(2, 4);
+    pressure = (float)p / 100.0;
+}
+
+void BMP085::init (BMP085_oss p_oss) {
+    ac1 = twi_readshort(WEATHER_BMP085, 0xaa);
+    ac2 = twi_readshort(WEATHER_BMP085, 0xac);
+    ac3 = twi_readshort(WEATHER_BMP085, 0xae);
+    ac4 = twi_readshort(WEATHER_BMP085, 0xb0);
+    ac5 = twi_readshort(WEATHER_BMP085, 0xb2);
+    ac6 = twi_readshort(WEATHER_BMP085, 0xb4);
+    b1 = twi_readshort(WEATHER_BMP085, 0xb6);
+    b2 = twi_readshort(WEATHER_BMP085, 0xb8);
+    mb = twi_readshort(WEATHER_BMP085, 0xba);
+    mc = twi_readshort(WEATHER_BMP085, 0xbc);
+    md = twi_readshort(WEATHER_BMP085, 0xbe);
+    oss = p_oss;
+}
+
+unsigned short BMP085::twi_readshort (int id, int addr) {
+    unsigned short i;
+
+    i2c.start();
+    i2c.write(id);
+    i2c.write(addr);
+
+    i2c.start();
+    i2c.write(id | 1);
+    i = i2c.read(1) << 8;
+    i |= i2c.read(0);
+    i2c.stop();
+
+    return i;
+}
+
+unsigned long BMP085::twi_readlong (int id, int addr) {
+    unsigned long i;
+
+    i2c.start();
+    i2c.write(id);
+    i2c.write(addr);
+
+    i2c.start();
+    i2c.write(id | 1);
+    i = i2c.read(1) << 16;
+    i |= i2c.read(1) << 8;
+    i |= i2c.read(0);
+    i2c.stop();
+
+    return i;
+}
+
+void BMP085::twi_writechar (int id, int addr, int dat) {
+
+    i2c.start();
+    i2c.write(id);
+    i2c.write(addr);
+    i2c.write(dat);
+    i2c.stop();
+}